The present invention relates to an electrophotographic image forming apparatus and a process cartridge (referred to as “cartridge” hereafter) that is attachable to and detachable from the electrophotographic image forming apparatus. Here, the electrophotographic image forming apparatus (referred to as “image forming apparatus” hereafter) forms an image on a recording material (recording medium) by using an electrophotographic image forming process. Examples of the image forming apparatus include a printer (such as a laser beam printer or an LED printer), a copier, a facsimile machine, a word processor, a multi-function device (multi-function printer) that has the functions of these devices, and so forth.
A process cartridge method that allows the cartridge to be attached to and detached from an apparatus main body of the image forming apparatus is adopted for a related-art image forming apparatus that uses the photoelectric image forming process. With this process cartridge method, electrophotographic photosensitive drum (referred to as “photosensitive drum” hereafter) and process devices that perform operation on the photosensitive drum are integrated with one another in a cartridge, so that maintenance of the image forming apparatus can be simplified.
In such a cartridge, the difference in thermal expansion occurs between a developing blade support plate and a developing frame due to, for example, changes in ambient temperature. This difference causes a problem in that the developing blade is bent. Thus, the difference in contact pressure at which the developing blade is in contact with a developing roller occurs between a central portion and end portions in the longitudinal direction. This may cause density unevenness in an image. In order to address this, a structure has been proposed in which a developing blade is secured to a developing frame by a stepped screw using a wave washer (PTL 1).